This invention relates to apparatus and methods for removing tops or roots from crops such as radishes.
Many purchasers demand that root crops be supplied with little or no tops or roots. In the distant past they were removed by hand using a blade. As will be explained hereinafter it is proving necessary to use this method again to meet the demands of some purchasers.
Mechanised crop toppers have been devised. They typically comprise a plurality of contra-rotating rollers with a small gap. At least some of the rollers have an upstanding helical bead or scroll formed on them. A very narrow gap extends between the tip of the bead and an adjacent roller. Material to be removed, for example, tops and roots are caught in this small gap or xe2x80x98nipxe2x80x99 and torn off. Unfortunately, especially if one wishes to crop the top or root close to the product, damage can ensue. For this reason some purchasers such as major supermarkets insist on manual removal of tops.
GB 2 313 284 (Richard Pearson Ltd) describes an agricultural separating device comprising a plurality of counter-rotating members. The counter rotating members comprise resiliently deformable starwheels.
GB 2 215 972 (N. A. Garford) describes a crop cleaning device comprising a plurality of counter-rotating spaced apart shafts. The shafts are provided with scrolls or flights.
JP 67 026 960 (Asahi Kasei Kogyo KK) describes a reinforced plastics pipe of twisted polygonal shape.
The invention seeks to overcome or reduce the problems associated with the prior art.
According to the invention there is provided a machine for removing roots and tops from crops the machine comprising a pair of counter-rotating rollers spaced apart so as to define a nip there between, and means for rotating the rollers characterised in that at least one roller is in the form of a polygonal twisted prism. Preferably, the polygonal twisted prism contains at least one full twist.
According to the invention there is provided a roller for a machine for removing the tops and roots of crops between the nips of a pair of counter-rotating rollers, the roller being in the form of a polygonal twisted prism.
According to the invention there is provided a method for removing the tops and roots of crops the method comprising;
providing at least one pair of counter-rotating rollers spaced apart so as to define a nip therebetween, and
introducing the roots or tops to the nip wherein at least one roller is in the form of a polygonal twisted prism.
It has unexpectedly been found that very good topping action can be obtained by twisting bar material. It is thought that the good results are a function of three features. First the bar corners are relatively sharp and provide a degree of cutting rather than the tearing action of the prior art rollers. Secondly there is a front clearance between the working edge and the body of the bar. This front clearance is almost absent in a cylindrical bar provided with a bead. The front clearance especially in a three or four sided bar is enhanced because bending the bar deforms the cross-section. In cross-section the initial planar faces of the bar become concave.
Thirdly the bar has, in effect, a multi-start helix.
The features allow more efficient removal of tops and roots. This allows the rotational speed of the rollers to be reduced by a factor of around 3 to 6 times while still allowing the same throughput. The reduction in rotational speed substantially reduces the probability of damage to the crop.